Python如何传递任意数量的实参
传递任意数量的实参
形参前加一个 * ，Python会创建一个已形参为名的空元组，将所有收到的值都放到这个元组中：
def make_pizza(*toppings):
print("\nMaking a pizza with the following toppings: ")
for topping in toppings:
print("- " + topping)
make_pizza('pepperoni')
make_pizza('mushroom', 'green peppers', 'extra cheese')
不管函数收到多少实参，这种语法都管用。
1. 结合使用位置实参和任意数量实参
def make_pizza(size, *toppings):
print("\nMaking a " + str(size) + "-inch pizza with the following toppings: ")
for topping in toppings:
print("- " + topping)
make_pizza(16, 'pepperoni')
make_pizza(12, 'mushroom', 'green peppers', 'extra cheese')
运行结果：
Making a 16-inch pizza with the following toppings: - pepperoni Making a 12-inch pizza with the following toppings: - mushroom - green peppers - extra cheese
2. 使用任意数量的关键字实参
def build_profile(first, last, **user_info):
profile = dict()
profile['first_name'] = first
profile['last_name'] = last
for key, value in user_info.items():
profile[key] = value
return profile
user_profile = build_profile('albert', 'einstein', location='princeton', field='physic')
print(user_profile)
形参**user_info中的两个星号让python创建了一个名为user_info的空字典。
Python中的返回值是什么
返回值
函数并非总是直接显示输出，相反，它可以处理一些数据，并返回一个或一组值。函数的返回值被称为返回值。
1. 简单的返回值
def get_formatted_name(first_name, last_name):
full_name = first_name + ' ' + last_name
return full_name.title()
musician = get_formatted_name('jimi', 'hendrix')
print(musician)
调用返回值的函数时，需要提供一个变量存储返回的值。
2. 让实参变成可选的
def get_formatted_name(first_name, middle_name, last_name):
full_name = first_name + ' ' + middle_name + ' ' + last_name
return full_name.title()
musician = get_formatted_name('john', 'lee', 'hooker')
print(musician)
然而并非每个人都有中间名，怎样让中间名变成可选呢？
def get_formatted_name(first_name, last_name, middle_name=' '):
if middle_name:
full_name = first_name + ' ' + middle_name + ' ' + last_name
else:
full_name = first_name + ' ' + last_name
return full_name.title()
musician = get_formatted_name('john', 'hooker', 'lee')
print(musician)
musician = get_formatted_name('jimi', 'hendrix')
print(musician)
给形参中间名一个空字符为默认值，将其移动至形参列表的末尾；调用函数时确保实参中间名方最后。
3. 返回字典
def build_person(first_name, last_name):
person = {'first': first_name, 'last': last_name}
return person
musician = build_person('jimi', 'hendrix')
print(musician)
扩展函数，使其接受可选值
def build_person(first_name, last_name, age=' '):
person = {'first': first_name, 'last': last_name}
if age:
person['age'] = age
return person
musician = build_person('jimi', 'hendrix', age=27)
print(musician)
4. 结合使用函数和while循环
def get_formatted_name(first_name, last_name):
full_name = first_name + ' ' + last_name
return full_name.title()
while True:
print("\nPlease tell me your name:")
f_name = input("First name: ")
l_name = input("Last name: ")
formatted_name = get_formatted_name(f_name, l_name)
print("\nHello, " + formatted_name + "!")
循环调用定义的函数，say hello everyone!!! 该在什么地方提供推出呢？
def get_formatted_name(first_name, last_name):
full_name = first_name + ' ' + last_name
return full_name.title()
while True:
print("\nPlease tell me your name:")
print("(enter 'q' at any time to quit)")
f_name = input("First name: ")
if f_name == 'q':
break
l_name = input("Last name: ")
if l_name == 'q':
break
formatted_name = get_formatted_name(f_name, l_name)
print("\nHello, " + formatted_name + "!")
每次提示用户输入时均可推出。
